The present invention relates to a fan assembly that includes a fan wheel or impeller driven by an electric motor.
The problem with such fan assemblies is that the electric motor must be cooled in a forced manner especially for higher output fans. To accomplish this, it is known to dispose an additional fan wheel on the motor shaft in order to achieve a cooling effect for the electric motor. However, on the one hand this requires additional mechanical expenditure, and on the other hand the efficiency of the fan assembly is impaired because for the small additional fan wheel, which has a relatively poor efficiency, a relatively great amount of drive energy must be used. It is therefore known to provide in the pressure region of the fan, at locations having a small dynamic pressure, intake openings in the forced air flow and to let the air that is drawn in at these locations pass by the electric motor in order to cool the same. However, the quantity of motor cooling air that can be provided in this manner is sufficient only for motors that either have a low output, or that provide for a relatively large pressure build-up and a correspondingly high dynamic differential pressure.
Attempts have therefore been undertaken to dispose in the forced air flow an air-collecting member, and to convey the forced air collected there to the electric motor as cooling air. However, this also greatly impairs the efficiency of the fan, since the air-collecting member not only branches off a portion of the forced air that is generated, but rather above all additional turbulence results that adversely affects the forced air flow.
It is therefore an object of the present invention to provide a fan assembly of the aforementioned general type where the electric motor can be cooled in an energy-favorable manner and independent of assembly.